I presume that JCCasper was either giving you a per-square (100 square feet = a "square") estimate, or he dropped a zero. As he said he was a roofer, he is probably so used to thinking of cost per square that he gave that number instead of the total roof area estimate.
Reroofing typically runs from a low of about $200 to as much as $1000+ per square - so $2000-10,000 for your size roof. The lower end being single-layer asphalt shingle tearoff with no sheathing work, minimal flashing, no drip edges, reuse existing draft hoods and vents, economy shingles from a rip and go contractor (who probably would not be licensed, bonded, and insured at that price). Around $350-450 is more normal, and the up to $1000+/square would be for a very steep roof with high-end slate roofing and a lot of dormers or chimneys to flash.